This invention relates to a disk brake having pads which are less liable to be unevenly abraded.
An ordinary disk brake comprises a disk and friction members adapted to be urged by a hydraulic brake piston into frictional contact with the disk. The piston is arranged so that the center of its biasing force is located on a line extending in a tangential direction of the disk and passing a center of frictional surface of the pad or offset therefrom toward the outer periphery of the disk to increase the braking force with a larger effective braking radius, If the friction member of each pad comprises a plurality of segments, the respective segments have individual centers of frictional surface.
In such a disk brake, in order to reduce uneven abrasion of the pads at the disk trailing side due to angular moment that acts on the pads when braking, the brake piston is arranged so that the center of its biasing force is offset toward the leading disk side from the center of frictional surface of the pad. With a brake in which each pad is urged by a plurality of pistons receiving the same fluid pressure, the piston at the leading disk side is adapted to have a larger pressure bearing area than the piston at the trailing side in order to smooth out the distribution of the surface pressure on the pad in a tangential direction.
With a disk brake having no means for preventing uneven abrasion, as shown in FIG. 4, if a brake piston 3 is inclined in the tangential direction of the disk and becomes stuck in a cylinder 2 due to uneven abrasion of the pad in the tangential direction of the disk, it becomes difficult for the piston to incline in the radial direction of the disk in the cylinder 2. Thus, uneven abrasion of a pad 4 in the diametric direction of the disk will not develop any further.
In contrast, with the above-described disk brake provided with means for preventing uneven abrasion, the piston can incline more freely in the cylinder in the diametric direction of the disk than the former piston. A conventional disk brake of this type has its piston arranged so that the center of its biasing force is located on a line extending in a tangential direction of the disk (in a direction perpendicular to a diametric direction) and passing the center of frictional surface of the pad or offset therefrom toward the outer periphery of the disk. Thus, the surface pressure on the pad will be distributed uniformly in a tangential direction of the pad or will be stronger at its portion near the outer periphery of the disk, Due to these factors, due and also to the difference in revolving speeds between inner and outer parts of the disk, the pad tends to be abraded more rapidly at portions near the outer periphery of the disk, Thus, as a whole, the pad is abraded unevenly to a considerable degree in a diametric direction of the disk,
it is therefore all object of the present invention to reduce uneven abrasion of the pad both in tangential and diametric directions of the disk.